State route 91 winds south from the hilly exurbs of Riverside County, a place of citrus orchards, indoor shooting ranges and Make-California-Great-Again signs. Turning off past Saddleback church, one of America’s largest megachurches, the road heads towards the richer, Democratic suburbs of coastal Orange County. At Huntingdon Beach, the congressman for the district, Dana Rohrabacher, is into his stump speech. “What a wonderful place to live,” he shouts. “But the quality of life will not survive if we have open borders and millions of …” His peroration is drowned out by the roar of the crowd. But the biggest noise in Californian politics is the gathering murmur of a Democratic wave. It could sweep away a decades-old Republican dominance of this area.